The present invention relates to a drill bit preferably a bit of the percussion type having a bit body of steel, the front of which is provided with one or several slots in which inserts of tough hard metal are attached by brazing.
With commonly available drill bits equipped with hard metal inserts, stresses occur between the hard metal insert and the steel material during brazing which under percussion impact are released and can lead to premature failure. The primary reason therefor is the difference in coefficients for linear expansion between the hard metal and the steel. It has been found that in rock formations that cause severe wear of the drill bit it is desirable to use cemented carbide grades of greater hardness which hitherto has been impossible due to the fact that they become too brittle due to the above-related braze stresses. The use of inserts of cemented carbide grades of higher hardness would also enable a reduction of the number of regrinding operations. Especially in long hole drilling operations it is desirable to drill as far as possible without having to interrupt the work for removing the drill for regrinding purposes.